PICcoder

Bill Of Materials For Ethernet Demo Board 

Design Title : Ethernet Demo Board
Author : Ian Horsley
Revision : 1.1
Design Created : 21 February 2006
Design Last Modified : 27 February 2006
Total Parts In Design : 35
 
 
10 Resistors
 
 Quantity:  References  Value 
 1  R1  2k7 
 1  R2  100k 
 4  R3-R6  50 
 3  R7-R9  180R 
 1  R10  10k 
 
14 Capacitors
 
 Quantity:  References  Value 
 4  C1, C2, C6, C7  22p 
 1  C3  10u 
 2  C4, C5  10n 
 6  C8-C13  0.1u 
 1  C14  0.01u 2kV 
 
3 Integrated Circuits
 
 Quantity:  References  Value 
 1  U1  PIC18LF4620 
 1  U2  ENC28J60 
 1  U3  16PT8515 
 
4 Diodes
 
 Quantity:  References  Value 
 1  D1  LED-GREEN 
 1  D2  LED-YELLOW 
 1  D3  LED-RED 
 1  D4  DIODE 
 
4 Miscellaneous
 
 Quantity:  References  Value 
 1  J1  RJ45 Connector 
 1  L1  Ferrite Bead 
 1  X1  25 Mhz 
 1  X2  24 Mhz  

The parts that I had most difficulty sourcing where the 25Mhz crystal and the Base-T Transformer which the ENC28J60 needs. In the end I removed them from an spare network card I had. The transformer chip was alittle tricky to remove. I removed as much solder as I could with a solder sucker and then heated the circuit board on an electric kitchen hob to pull the chip out with pliers (warning be careful of burning yourself if you attempt this!!!). The 0.01uF 2kV capacitor is also often found on network cards and is easily removed.

Without using an SPI eeprom it is important to remember that the website has to be stored in the program memory of the PIC, a large PIC such as the 18LF6420 or 18LF8722 should have enough space for the example website. If the website is not included then a smaller PIC could be used.

The 5 decoupling capacitors should be placed between the pairs of Vdd and Vss pins on the ENC28J60 chip and as close to the chip as possible. Look at the pinout in the data sheet to determine which pins are the pairs and place the capacitors as close to the chip as possible.  The ferrite bead inductor is simply a piece of wire through a ferrite bead, wound through multiple times if the bead is large.

The 1:1 turns ratio transformer seems to have a standard pinout with 12 pins and 4 blanks, at 10Mbits all the transforms I have tried have worked fine, dispite having slightly different internal configurations. Some computer ethernet cards may contain the transformer and 0.01uF 2kV capacitor built into the RJ45 connector. Just find the datasheet for your part and wire it up accordingly.